Effect of exercise on protein turnover in muscles of lean and obese mice

Abstract

The effect of work-induced hypertrophy on skeletal muscle protein metabolism was studied in lean mice and in mice rendered obese with goldthioglucose. After tenotomy of the gastrocnemius muscle, the adaptative growth of soleus muscle was less pronounced in obese than in lean mice. Protein turnover was studied in the isolated soleus muscle 4 days after the operation. Tyrosine incorporation in total proteins and tyrosine release in the incubation medium (indices of protein synthesis and degradation) were increased by 3- and 2-fold in overloaded (i.e. work-induced hypertrophied) muscles of lean and obese mice, respectively, compared to the control muscles isolated from the non-operated leg. The qualitative modifications in the pattern of proteins synthetized from 35S-methionine were identical in both groups of mice. This increase in protein turnover in overloaded muscles results from an increased rate of polypeptide chain initiation (3-fold in lean mice, 2.2-fold in obese mice) without any modification of peptide chain elongation rates. Work-induced hypertrophy was also able to reverse the defect in amino acid uptake which is present in soleus muscles of GTG-obese mice. These results suggest that the work-induced increase of skeletal muscle protein turnover is diminished in obese mice.

Novel insights into the regulation of skeletal muscle protein synthesis as revealed by a new nonradioactivein vivotechnique

“…The results show that the EV-SUnSET technique was indistinguishable from a standard radioactive-based technique for detecting the SA-induced increase in protein synthesis. The ex vivo SA-induced increase in protein synthesis observed in this study is also very similar to that previously reported in the SOL muscle ex vivo, using radioactive labeling (13). Notably, when applied in vivo, our IV-SUnSET technique also detected the SA-induced increase in protein synthesis, and the magnitude of this effect was not significantly different from that detected ex vivo.…”

“…It has been proposed that SA promotes an increase in protein synthesis via both enhanced translational capacity (rRNA) and translational efficiency (rate/rRNA) (12,13). Consistent with this hypothesis, we found that the SAinduced increase in protein synthesis (3.6-fold) greatly exceeded the increase in 28S and 18S rRNA concentration (2.2-fold; Fig.…”

Regulation of Mg2+ uptake in isolated rat myocytes and hepatocytes by protein kinase C

“…Vasopressin, and to a lesser degree carbachol, result in enhanced activity of phospholipase C and D [41,42], leading to an accumulation of diacylglycerol and stimulation of PKC activity. They also activate Ca 2+ mobilization through IP3 formation, and to a lesser extent, inhibit cAMP formation by activating G~ proteins.…”

Influence of adiposity (genetic or hormonal) on the metabolism of amino acids and nutritional responses

“…Simultaneous experiments were performed to study amino-acid metabolism and hormonal modifications induced by obesity. Insulin is more active in lipogenesis than in proteinogenesis in Zucker rats which have been previously treated with alloxan (Chan et al, 1982;Stolz an Martin, 1982 (Monier et al, 1983;Augert et al, 1986).…”